Grabb said he could not tell whether the miniature limbs were from a benign stem cell tumor called a teratoma or the remnants of an identical twin that did not split off and survive, a condition called fetus in fetu.

"It looked like the breach delivery of a baby, coming out of the brain," Grabb told The Associated Press. "To find a perfectly formed structure is extremely unique, unusual, borderline unheard of."

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Previously on Neatorama: Fetus in Fetu: the Male Pregnancy